On Wednesday, March 11, 2015 at 11:37:05 PM UTC-4, DoN. Nichols wrote:
On 2015-03-11, Martin Eastburn wrote:
The real isolation method is the flywheel method. Electrical to
mechanical that doesn't change with fluctuations.

AC mains drive massive multi-ton rock that spins. On that shaft is a
AC (generator) alternator. It generates the AC in single or three
phase. If the external AC shuts down, the rock keeps turning. It
turns for a long time without input power. So brown outs and twinkles
are never seen on the real load because the rock absorbs small and large
changes.

Cray Research used them for their buildings. Massive spinning disks of
rock.

Martin - been there, seen it.

Well ... our lab had something similar to make sure that the
fume hoods would not suddenly stop when some rather toxic gasses were in
use there. It also protected the rest of the building, too.

But -- it was not a separate motor and generator. Instead, a
*big* permanent magnet rotor three-phase motor kept the flywheel (steel,
not rock in this case) spinning. About 4' diameter by about 8" thick,
IIRC.

On the other side of the flywheel was a flexible coupling, an
electro-magnetic clutch (brake assembly from a B-58 I believe) and a big
Detroit Diesel.

A cabinet of electronics monitored the power. If the frequency
or voltage drifted out of spec, the clutch was allowed to
transmit torque, and the flywheel started the Diesel *right* *now*.
In the meanswhile, the permanent magnet rotor three phase motor
became a generator, and kept the building going. The flywheel for a little
while, and then the Diesel

Now there were three *big* breakers on a panel.

And at demo time, those breakers and that 500 wire and bus bars aren't bad for spending change.